Fix extra comma error in list of projects

[Jimilian]

Right now user can provide list of project with extra comma. I.e. "projectA, "
And verification passes.

But after execution user receives:

ERROR: Build aborted. Can't trigger undefined projects. 1 of the below project(s) can't be resolved:
 > 
 > projectA
Check your configuration!

It happens because in TriggerBuilder.java we have check like this:

// Get the actual defined projects
StringTokenizer tokenizer = new StringTokenizer(config.getProjects(env), ",");
...
if (tokenizer.countTokens() != projectList.size()) {

And as result number of tokens are bigger than number of projects (because we skipped empty one before). So, I adjust this check with the most earliest existed check I found.

[Jimilian]

@olivergondza, please, review :)

[olivergondza]

Looks, good to me (https://github.com/jenkinsci/parameterized-trigger-plugin/pull/111/files?w=1) but is missing tests.

[Jimilian]

@kwhetstone, can you merge, please?

[oleg-nenashev]

I would rather return another warning ("Blank job name in the list")

[Jimilian]

All other messages are using hudson.tasks.Messages from core. And most of them are localized. Is it ok to put custom message? It could break user's expectations.

[oleg-nenashev]

It's a new message, so IMHO it's fine. Jenkins core just skips such empty lines without any message:

public static <T extends Item> List<T> fromNameList(ItemGroup context, @Nonnull String list, @Nonnull Class<T> type) {
        final Jenkins jenkins = Jenkins.getInstance();
        
        List<T> r = new ArrayList<T>();
        if (jenkins == null) {
            return r;
        }
        
        StringTokenizer tokens = new StringTokenizer(list,",");
        while(tokens.hasMoreTokens()) {
            String fullName = tokens.nextToken().trim();
            if (StringUtils.isNotEmpty(fullName)) {
                T item = jenkins.getItem(fullName, context, type);
                if(item!=null)
                    r.add(item);
            }
        }
        return r;
    }